BRPI0620973A2 - tiltable rotor hub with rigid gimbal in the plane of rotation - Google Patents

Abstract

TILING ROTOR HUB WITH RIGID CARDAN JOINT IN THE ROTATION PLAN. The present invention discloses a rotor hub for a rotary-wing aircraft. The rotor hub comprises a crosspiece comprising a plurality of crosspiece arms and a plurality of crosspiece bars, in which the crosspiece arms are joined to each other by the crosspiece bars, and in which a plurality of internal crosspiece walls define a central empty space. A pitch camshaft is movably connected to the crosshead and a portion of the pitch camshaft is located within the central void. A connection housing is fixedly connected to the crosshead.

Description

Invention Patent Descriptive Report for "ROTOR CUBE LEANED WITH RIGID CARDAN JOINT ON ROTATION PLAN".

Technical Field

The present invention relates to the field of tilt rotor aircraft rotor hubs. Specifically, the present invention relates to a gimbal pivotable rotor hub rigid in the plane of rotation.

Description of the prior art

Rotor hubs have been in use for many years. There are numerous designs of rotor hubs with great results for the most varied rotary wing aircraft. Rotor hubs are generally designed to be a means of connecting rotor blades to a rotating shaft or mast and are therefore particularly suited to this function.

Those of skill in rotary-wing aircraft design typically classify rotor hubs into two main categories: "stiff-in-plane" and "soft-in-plane" ). The rigid rotor hub in the plane of rotation is used on a rotary-wing aircraft when the natural frequency of forward / reverse / rotor blade plane vibration is greater than the rotor rotational frequency and the natural frequency of beat / out vibration. rotor blade plane. The flexible rotor hub in the plane of rotation is used when the natural frequency of forward / reverse vibration / rotor blade plane is less than the rotor rotational frequency and the natural frequency of beat vibration / out of plane blade rotor. rotor. We know that the rotor blades and associated rotor hub of a rotary-wing aircraft become more dynamically unstable as the natural frequencies of rotor blade beat / off-plane vibration and forward / reverse vibration / in the plane of the rotor blades converge to equal values. Therefore, rotary-wing aircraft are often designed so that the natural frequencies of beat / out-of-plane rotor blade vibration and forward-reverse / in-plane rotor blade vibration maintain a minimum separation of approximately 25 % of rotor rotational frequency.

When choosing between rigid plane of rotation and flexible plane of rotation, a number of high-level generalizations are often taken into account when designing a rotary-wing aircraft. The combined weight of the rotor hub and rotor blades of a rigid rotary-wing aircraft in the plane of rotation is generally greater than the combined weight of the rotor hub and rotor blades of a flexible rotary-wing aircraft in the plane of rotation. rotation. However, nowadays the rigid set of components in the plane of rotation is regarded as the best solution for traveling at high speeds and / or producing greater thrust while maintaining dynamic vibratory stability with greater control. One of several variables involved in achieving the desired dynamic vibratory stability for the rotor hub and rotor blades of a rigid rotary-wing aircraft in the plane of rotation is angle δ3. Figure 1 (state of the art) shows a schematic view of a rotor hub illustrating the angle δ3 to a rotor system. Since one end of the pitch camshaft is restricted by the pitch camshaft and the other end of the camshaft is connected to the paddle, a pitch change will occur with paddle stroke. For this reason, the angle δ3 represents a correlation between rotor beat and rotary wing pitch. As the rotary wing pushes upwards, a rotor system with a positive δ3 angle will experience a mincing pitch, while a rotor system with a negative δ3 angle will experience a pitch pitch. Angle δ3 is manipulated to provide dynamic stability and also to reduce rotor beat ranges during burst and / or pilot maneuver disturbances. As an example, the angle δ3 on a three-bladed tilt rotor aircraft is generally adjusted to values close to -15 degrees, which provides an adequate level of stability and beat attenuation.

Demand is increasing for rotary-wing aircraft capable of higher thrust, higher speeds and heavier loads. For example, there is a need for more powerful tilt-rotor aircraft. One way to produce more thrust is to increase the number of rotary wings. Current tilt rotor aircraft use three-blade rotor systems. In three-blade rotor systems, the pitch camshaft and the pitch camshaft (see Figure 1 - State of the Art) are usually located in the plane with the rotor hub and outside the rotor hub. However, it is a major challenge to obtain reduced δ3 angles (for example, δ3 angles close to -15 degrees) for a multi-blade rotor containing four or more blades while locating the camshaft and the step cam generally in the plane with the hub and outside the hub. The rotor hub configuration as described above for multi-blade rotor systems does not allow the pitch camshafts to be located in proper positions due to structural interference. In addition, it is widely recognized by those skilled in the art of rotary-wing aircraft design the need to configure the rotor assembly of rotor systems so as to be as close as possible to the rotational geometry axis to minimize unwanted resulting forces which lead to premature component failure.

While advances in the rotor hub described above represent symbolic developments in rotor hub design, considerable shortcomings still remain.

Summary of the Invention There is a need for a rotor hub.

perfect.

Therefore, it is an object of the present invention to provide an improved rotor hub allowing connection to four or more rotor blades while maintaining optimal δ3 angles.

This objective is achieved by means of a rotor hub in which both the pitch camshafts and the pitch camshafts are located within an internal gap of the rotor hub. For example, the rotor hub may be configured: (1) with a connection housing located above the yoke crosshead (2) with a connection housing located below the crosshead; and (3) having two connecting housings, one of the connecting housings being located above the crosshead and the other being located below the crosshead.

The present invention offers significant advantages, among which: (1) it allows the use of more than ten blades in a rotor system of a tilt rotor aircraft; (2) reduces the risk of damage to the camshaft caused by fragments or ballistic attacks; (3) reduces the risk of damage to the camshaft caused by fragments or ballistic attacks; (4) provides hub spring redundancy; and (5) improves force transfer between hub springs and crosshead.

Other objectives, aspects and advantages are apparent from the following written description. Brief Description of the Drawings

The novel features taken as characteristic of the invention are set forth in the appended claims. However, the invention itself, as well as a preferred mode of use, and other objects and advantages thereof, will be better understood by reference to the following detailed description, when read in conjunction with the accompanying drawings, in which:

Figure 1 (State of the Art) is a simplified schematic representation of the effect of angle δ3 on a rotor system;

Figure 2 is an elevation view of a tiltable rotor aircraft containing a rotor hub according to the preferred embodiment of the present invention;

Figure 3A is a perspective view of the rotor hub used in the tilt rotor aircraft of Figure 2;

Figure 3B is a perspective view of the rotor hub crosspiece of Figure 3A;

Figure 4 is a perspective view of the rotor hub of Figure 3A with the connection housing removed;

Figure 5 is a top view of the rotor hub of Figure 3A with the connection housing removed;

Figure 6 is a top view of the rotor hub of Figure 3A;

Figure 7 is a cross-sectional view of the rotor hub of Figure 3A along line 7-7 of Figure 3A; Figure 8 is a partial perspective view of a rotor hub containing a connecting housing located under the crosshead in accordance with an alternative embodiment of the present invention;

Figure 9 is a cross-sectional view of the rotor hub of Figure 8 along line 9-9 in Figure 8;

Figure 10 is a perspective view of a rotor hub containing two connecting housings in accordance with an alternative embodiment of the present invention; and

Figure 11 is a cross-sectional view of the rotor hub of Figure 10 along line 11-11 in Figure 10.

Description of Preferred Embodiment

The present invention is an improved rotor hub that allows connection to four or more rotary wings while maintaining optimal δ3 angles. There are three main embodiments of the invention: (1) with a connecting housing located above the crosshead; (2) with a connection housing located under the crosshead; and (3) having two connecting housings, one of the connecting housings being located above the crosshead and the other being located below the crosshead. However, the scope of the present invention is not limited to the specific embodiments disclosed herein and illustrated in the drawings. The rotor hub of the present invention allows the incorporation of four-blade rotor systems in a tilt-rotor rotary-wing aircraft. However, while specific reference is made to the use of the present invention with tilt-rotor rotary-wing aircraft, the present invention may alternatively be used with any other rotary-wing vehicle / aircraft. In addition, the rotor hub of the present invention may alternatively be used with a rotary system containing more or less than four rotary wings.

Figure 2 illustrates a tilt-rotor rotary-wing aircraft incorporating the rotor hub of the present invention. Figure 2 illustrates a tilt rotor aircraft 11 in "airplane" flight operation mode. Wings 15, 17 are used to support the body of aircraft 13 in response to the action of rotor systems 19, 21. Each rotor system 19,21 is illustrated as containing four rotary wings 23. Nacelles 25, 27 substantially enclose the rotor hubs 29, covering the rotor hubs 2 in the view of Figure 2. Of course, each rotor system 19, 21 is driven by a motor (not shown) substantially housed within each nacelle 25, 27, respectively.

Figure 3A illustrates a perspective view of the preferred embodiment of rotor hub 29 of the present invention. Rotor hub 29 is illustrated as comprising a crosshead 31 having crosshead arms 33 and crosshead bars 35. Crosshead arms 33 are integrally connected to crosshead bars 35. In one embodiment, crosshead 31 is constructed of composite materials. More specifically, the crosshead 31 is constructed of a plurality of separate joined layers composed of directional fiber material. However, crosshead 31 may alternatively be constructed of any other suitable material in any suitable manner. In addition, although crosshead 31 is illustrated as containing four crosshead arms 33, other rotor hub configurations according to the present invention may comprise more or less than four crosshead arms 33 for connection to more or less than four wings. 23, respectively.

The rotor hub 20 is illustrated in detail with representative geometric pitch shifting axes 37A, 37, around which the pitch of the rotary wings 23 (see Figure 2) is altered. In addition, the rotor hub 29 is illustrated with a representative geometric axis of rotation of the mast 39, around which a mast (not shown) is rotated when driven by an operably associated transmission (not shown).

Outer flange bearings 41 are connected to the outermost portions of the crosshead arms 33. Outer flange bearings 41 allow at least a certain degree of rotation of the rotary wings 23 around the pitch shifting axes 37A, 37B. Centrifugal Force Bearings (CF) 43 are connected to external flagging bearings 41. CF 43 bearings are the primary intermediate connecting devices between rotary wings 23 and rotor hub 29. CF 43 bearings support the generally huge centrifugal force generated. by the rotary wings 23 rotating about the rotation axis 39 of the mast. Figure 3B illustrates a simplified view of crosshead 31 of rotor hub 29. A central void 30 is defined by the inner walls 32 of crosshead 31.

As shown in Figure 7, hub spring 45 includes an inner core 47 comprising a first series of several alternately stacked rubber members and metal shim elements (not shown in detail) interspersed between an upper outer connector housing 49 and a inner casing 51, and a second series of several alternately stacked rubber members and metal shim elements interspersed between a lower outer casing 50 and another inner casing 51. Casings 49-51 are illustrated as being constructed of metal. Hub spring 45 allows crosshead 31 to pivot with respect to the mast and the rotational geometry axis 39 of the mast. Hub spring 45 also accommodates rotary wing beat 23 and transfers thrust.

As can be seen most clearly from Figure 4, wherein the rotor hub 29 is illustrated without the connection housing 49, the rotor hub 29 further comprises four camshafts of step 53. The camshafts of step 53 comprise arms 55 camshafts and internal beams 57 of the camshaft. The camshafts of step 53 are rotatably connected to the bores 59 through the inner flagging bearings 61. The inner flagging bearings 61 are substantially centered along the corresponding geometric pitch shifting axes 37 A, 37B. Inner flag bearings 61 are operably associated with similarly sized openings in the camshafts of step 53 located substantially at the intersection of the camshaft arms of step 55 and the inner joists of the camshaft of step 57. Handles (not shown) ) are connected to the inner beams of the camshaft of step 57 so that when the camshafts of step 53 are rotated around their respective corresponding geometry shifts 3 7 A, 37B, the handles make the wings (shown in Figure 2), which are connected to the handles, rotate correspondingly around the step change geometric axes 37A, 37B. The ends 63 of the camshafts of step 53 are illustrated as being located in a neutral / nominal position when the ends 63 are substantially centered around the plane created by the step shifting geometry axes 37A, 37B. The ends 63 of the camshafts of pitch 53 are connected to the upper ends of the pitch rods 65. The pitch rods 65 are rod-like elements oriented substantially parallel to the geometric axis of rotation of the mast 39. The movement of the rods step 65 in either direction along a path parallel to the geometric axis of rotation of the mast 39 raises or lowers the ends 63, thereby rotating the camshaft arms of step 55 and the inner beams of the camshaft 57 around its step change geometry axes 37 A, 37B, finally changing the pitch of the rotary wings 23. The camshafts of step 53 are located substantially within the central void 30. A central void column is defined as extending the vertical boundaries of the central empty space 30 both up and down and represents the vertical footprint of the central empty space 30. For example, the central empty column occupies at least the space between upper occupied area 34A and lower occupied area 34B, as illustrated in Figure 3B. In this embodiment, the arms 55 extend out of the central empty column. However, in other embodiments of the present invention, the arms 55 may alternatively remain within the central empty column.

As can be more clearly seen from Figure 5, where a top view of the rotor hub 29 is illustrated without the connecting housing 49 and the lower outer housing 50, the rotor hub 29 further comprises a homokinetic gasket (not shown in FIG. which comprises drive joints 67. Drive joints 67 are oriented substantially parallel to the plane created by the pitch shifting axes 37A, 37B. One end of each drive pivot 67 is adapted for connection to a trunnion (not shown) grooved to the mast / drive shaft (not shown). The trunnion transfers the rotational force from the mast to the drive joints 67. The other end of each drive joint 67 is adapted for connection with drive legs 68 of the connection housing 49 (see Figures 10 and 11), which transfer the force. of the drive joints 67 to the connection housing 49. The connection housing 49 is connected to the crosshead 31 along the bars of the crosshead 35, so that the rotational force is transferred from the connection housing 49 to the crosshead 31. A Figure 6 shows a top view of the rotor hub 29, while Figure 7 shows a cross-sectional view of the rotor hub 29 along line 7-7 of Figure 3A corresponding to the step shifting axis 37A, 37B .

Referring now to Figures 8-9 in the drawings, an embodiment of the rotor hub according to the present invention also incorporates a hub spring 71, similar to hub spring 45. Meanwhile, the hub spring connecting housing 72 45 is located below a crosshead 73. As illustrated in Figure 8, rotor hub 69 is substantially similar to rotor hub 29 and comprises substantially similar components, with three main differences: (1) the connection housing 72 is located on the lower side of crosshead 73 rather than upper side of crosshead 73; (2) The camshafts of step 75 are curved rod-like structures whose parts are located slightly above the plane created by the geometric shifting axes of step 77A, 77B but still within a central void defined by the inner walls 32. from crosshead 32; and (3) the drive joints 81 are shown to be located slightly below the plane created by the pitch shifting axes 77A, 77B, but still substantially within the central void column. It will be appreciated that the rotor hub 69 may alternatively comprise camshafts of step 53 situated substantially within the plane created by the geometrical shifting axes 77A, 77B. Similar to the embodiment of Figures 3 to 7, hub spring 71 permits pivoting of crosshead 73 with respect to the mast and the axis of rotation of the mast 39 (shown in Figure 3A). Hub spring 71 also accommodates rotary wing beat 23 (shown in Figure 2) and transfers thrust.

Referring now to Figures 10-11 in the drawings, an embodiment of the rotor hub according to the present invention containing a hub spring 85 comprising two connecting housings 86 is illustrated. As illustrated in Figure 10, rotor hub 83 is substantially similar to rotor hub 29 and comprises substantially similar components, except that two connector housings 86 are present within the rotor hub 83. One connection houser 86 is mounted on the underside of crosshead 87, while another connection housing 86 is mounted on the upper side of crosspiece 87. An important advantage of rotor hub 83 is the redundancy of connection housing 86. For example, if one of the connection housings 86 If damaged by a ballistic projectile or for some reason it fails, the remaining connection casing 86 may continue to function normally. Another important advantage of an embodiment including two connecting housings 86 is the resulting improved distribution of forces being transferred from the hub springs 85 to the crosshead 87. Similar to the embodiment of Figures 3 to 7, the hub springs 85 allow the crosshead to be pivoted 87 with respect to the mast and the mast axis of rotation 39 (shown in Figure 3A). Hub springs 85 also accommodate the rotating wing beat 23 (shown in Figure 2) and transfer thrust.

An important advantage of the present invention is that while allowing the use of four or more rotor wings per rotor hub, most components are compactly accommodated substantially within the internal void space between the crosshead arms. This arrangement makes the rotor hubs of the present invention a more enemy resistant target and less prone to unwanted debris. In addition, the present invention permits various variations in the displacement of the camshaft. For example, when a connection housing is located just at the top of a crosshead, there is more space available for downshifting the pitch camshaft. Similarly, when a connecting housing is located only on the underside of a crosshead, there is more space available for upshifting the pitch camshaft. In addition, when the connection housings are located at both the top and bottom of a crosshead, the pitch camshaft offset can be more evenly divided between upward and downward displacement. Finally, in each of the embodiments described above, a failure in CF bearing generally does not result in the loss of a rotary wing. Instead, the pitch camshaft associated with the failing CF bearing would be shifted to the associated crosshead shim so that, at least temporarily, safe operation of the aircraft could occur.

It is clear that an invention with significant advantages has been described and illustrated. Although the present invention is presented in a limited number of forms, it is not limited to just such forms, remaining open to various changes and modifications without departing from its essence.

Claims (20)

1. Rotor hub for a rotary-wing aircraft, comprising: a crosshead containing a plurality of crosshead arms, adjacent crosshead arms being joined together by a crossbar, crosshead arms and crossbar. crosshead defining a central void space, the void being adapted to receive a central mechanical axis through it; at least one pitch camshaft containing an internal pitch camshaft beam and a pitch camshaft arm, wherein the camshaft is pivotally connected to the crosshead and the camshaft inner beam step command is arranged substantially within the central void space; and a homokinetic joint adapted to transfer force from the central mechanical axis to the crosshead, and wherein the homokinetic joint is substantially disposed within an empty central column. Rotor hub according to Claim 1, characterized in that the crosshead is constructed of distinct layers of directional fiber material. Rotor hub according to claim 1, characterized in that it further comprises: a hub spring containing a first outer connecting housing resiliently connected to the crosshead. Rotor hub according to claim 3, characterized in that it further comprises: a second hub spring containing a second outer connecting housing resiliently connected to the crosshead. Rotor hub according to Claim 1, characterized in that the homokinetic joint comprises a drive joint disposed substantially within the central void space. Rotor hub according to Claim 1, characterized in that the pitch camshafts are configured to produce an angle δ3 of approximately -15 degrees. Rotor hub according to Claim 1, characterized in that the crosshead is configured to accommodate at least four rotary wings. Rotor hub according to Claim 1, characterized in that the rotor hub is configured for use with a tilt rotor aircraft. Rotor hub for a rotary-wing aircraft, comprising: a crosshead containing at least four crossheads, each pair of adjacent crosshead arms being joined together by a crosshead bar, the crosshead arms and the bars a crosshead defining a central void, the central void being adapted to receive a central mechanical axis through it; a step camshaft containing an inner step camshaft beam and a step camshaft arm, wherein the step camshaft is pivotally connected to the crosshead and the camshaft inner camshaft step is disposed substantially within the central empty column; and a homokinetic joint adapted to transfer force from the central mechanical axis to the crosshead, the homokinetic joint being substantially disposed within the central empty column; and wherein the pitch camshafts are configured to produce an angle δ3 of about -15 degrees. Rotor hub according to Claim 9, characterized in that the crosshead is formed from a composite material constructed of distinct layers of directional fibers. Rotor hub according to claim 9, characterized in that it further comprises: a first hub spring elastically coupled to the crosshead. Rotor hub according to Claim 11, characterized in that it further comprises: a second hub spring elastically coupled to the crosshead. 13. A rotary-wing aircraft, characterized in that it comprises: a fuselage; at least one engine loaded by the fuselage to provide torque; at least one rotary wing; a central mechanical shaft for transmitting torque to the rotary wing; and a rotor hub coupled between the central mechanical shaft and the rotary wing, the rotor hub comprising: a crosshead containing a plurality of crosshead arms, adjacent crosshead arms being joined together by a crossbar, crosshead arms and crosshead bars defining a central void, the void being adapted to receive the central mechanical axis through it; a step camshaft containing an inner step camshaft beam and a step camshaft arm, wherein the step camshaft is pivotally connected to the crosshead and the camshaft inner camshaft step is disposed substantially within a central void space; a first hub spring comprising a first outer connecting housing being fixedly connected to the crosshead; and a homokinetic joint coupled between the central mechanical axis and the crosshead, wherein the homokinetic joint is disposed substantially within a central empty column. Rotary-wing aircraft according to claim 13, characterized in that the crosshead is constructed of distinct layers of directional fiber material. A rotary wing aircraft according to claim 13, further comprising: a second hub spring comprising a second outer connecting housing, wherein the second outer connecting housing is fixedly connected to the crosshead. Rotary-wing aircraft according to claim 13, characterized in that the pitch camshaft is adapted to produce an angle δ3 of approximately -15 degrees. Rotary-wing aircraft according to Claim 13, characterized in that the crosshead is operably associated with at least four rotary wings. Rotary-wing aircraft according to Claim 13, characterized in that it is a tilt-rotor aircraft. A method for adjusting the pitch of a rotary wing, comprising the steps of: providing a crosshead containing a plurality of crosshead arms, the adjacent crosshead arms being joined together by a crosshead bar; and rotating a pitch camshaft located in a central hollow column by translating a pitch pivot into the central hollow column, wherein rotating the camshaft adjusts the pitch of a rotary wing. A method according to claim -19, further comprising the step of: providing a homokinetic joint comprising drive joints located within the central empty column.